This invention relates to an open-end friction spinning machine having a plurality of spinning units. Each spinning unit has two friction rollers that are arranged next to one another, form a wedge-shaped yarn forming gap and are driveable in the same rotational direction by means of a belt drive. Each spinning unit also has a feeding and opening device for the fiber material to be spun, at least one suction device aimed into the wedge-shaped gap and a withdrawal device for withdrawing the spun yarn from the wedge-shaped gap.
In the case of one single spinning unit, it is known to interrupt the continuous feeding of fiber material after a yarn breakage without disengaging the drives of other elements, such as a joint drive for the two rollers. It happens frequently, however, in the case of yarn breakage, that fiber or fiber residues still remain in the region of the wedge-shaped gap. These fibers continue to be twisted together without being withdrawn from the region of the wedge-shaped gap. The result is a very hard, yarn-type structure that creates a danger of damage to the rollers and/or their bearings, such as the deformation of the surface portions of the rollers.
One objective of this invention is to equip an open-end friction spinning machine having a plurality of spinning units with an operationally effective drive for the rollers that is as simple as possible. Another objective is to make it possible to disengage this drive at one single spinning unit without impairing the drive of the adjacent spinning units.
These objectives are achieved by providing a joint belt drive for at least those spinning units that are arranged on one machine side, and by equipping each spinning unit with means for disengaging the belt drive from that spinning unit. The disengaging means comprise at least one spring-loaded tension pulley holding the belt drive in the driving position, and locking means for locking the pulley in a position wherein the pulley holds the belt drive in the driving position. When the locking means is unlocked, the tension pulley automatically moves into an inoperative position wherein the belt drive is released from the driving position.
The use of a joint belt drive for the rollers of the spinning units of at least one side of the machine results in a simplification of the whole open-end friction spinning machine. By using one or more tension pulleys in the area of each spinning unit with the operational position of the tension pulleys being secured by locking means, it is possible to open only one of the locking devices and thereby disengage the drive at only one single spinning unit, without interferring with the belt drive of adjacent spinning units. The locking means is designed such that opening requires no special expenditure of force. In this way the opening of the locking means and thus disengaging of the drive can be carried out simply and rapidly.
According to an advantageous aspect of preferred embodiments of the invention, it is provided that the locking means is connected to a yarn guard in such a way that the locking means opens when activated by the yard guard. This ensures that when yarn breakage occurs, the drive of the rollers of the corresponding spinning unit will be interrupted immediately so that danger of damage to the spinning unit is avoided.
According to another advantageous aspect of preferred embodiments of the invention, each spinning unit is provided with a locking lever connected to the tension pulley that can be operated from an exposed side. The locking lever is brought into a locking position and secured in the locked position by a locking means. A source of potential energy is connected to the locking even in such a manner that upon opening the locking means, energy will be released so as to move the locking lever into a position which in turn forces the connected tension pulley into a disengaged position. The source of potential energy may be for example a spring means attached to a frame and in a high energy configuration. For the disengagement of the drive, only the locking means need be actuated and only by a relatively small force, wherein the source of potential energy will then supply a force that is sufficient to disengage the belt drive. It is especially advantageous to employ as the locking device, an electric control element, especially a switching magnet, which preferably moves transversely to the direction of motion of the locking lever. This electric control element therefore does not act directly against the force of the energy accumulator so that it does not require excessive switching forces itself.
According to another advantageous aspect of preferred embodiments of the invention, a locking lever is connected through a transmission mechanism with a holder carrying a tension pulley such that, after opening of a locking means the locking lever is moved by a source of potential energy and in turn moves the holder with the tension pulley into an inoperative position. In this arrangement it is contemplated by means of a transmission mechanism to direct the forces of the potential energy source and of the spring element loading the tension pulley in the operational position such that they do not directly oppose one another.
In certain preferred embodiments of the invention a tangential belt moving in the longitudinal direction of the machine is provided as the belt drive for the rollers. Such a tangential belt requires the minimum number of individual parts for the individual spinning units as well as for the drive. In this case, it is particularly advantageous that the tangential belt runs along directly in contact with the surface portions of the rollers. As a result, the rollers are driven by the tangential belt directly at the desired speed without the occurrence of any multiplication. It is also particularly advantageous that the axis of rotation of the tension pulley be parallel to the axes of rotation of the two roller and be arranged in the plane which bisects the wedge-shaped gap between the two rollers. This arrangement has the advantage that by means of a single tension pulley, the tangential belt is loaded evenly in the area of the two rollers. It is advantageous for the holder of the tension pulley to be provided with a lift-off roll which, with respect to the tangential belt, is arranged on the side opposite the tension pulley. By means of this lift-off roll, the tangential belt is lifted off the rollers so that is is totally removed from the surface of the rollers.
According to another advantageous aspect of preferred embodiments of the invention, each spinning unit is provided with valve means which can shut off or apportion a vacuum source in the area of the wedge-shaped gap. It is advantageous to actuate the valve controlling the vacuum source when a yarn breakage occurs for the purpose of turning off the vacuum, thus preventing more fibers from being transported into the area of the wedge-shaped gap. To apportion the effect of the vacuum source is especially advantageous when a subsequent yarn piecing process is carried out because it can be used to control the yarn forming process during the piecing operation.
In order to interrupt the vaccum source as well as stop the rollers, the valve is arranged and/or the locking lever is constructed in such a way that the valve is actuated by movement of the locking lever caused by the opening of the locking device.
According to another advantageous aspect of preferred embodiments of the invention, a movable servicing apparatus is provided that can be applied to a spinning unit in need of servicing, said apparatus containing means for returning the locking lever of this spinning unit into the locking position. Such a servicing apparatus, which is provided for carrying out a fully automatic yarn piecing process, has the capability of putting the source of potential energy back into a high energy configuration, thus restoring the operational position of the belt drive of the rollers of the corresponding spinning unit at a suitable point in time during the yarn piecing process. If, by means of a mechanical control, the vacuum source is turned off and the drive of the rollers is disengaged simultaneously due to a yarn breakage, it is necessary to return the locking lever very early during the piecing process into its operational position. In order to control the drive during the piecing process by means of the servicing apparatus, it is advantageous if the servicing apparatus is equipped with means for interrupting the driving effect of the belt drive at a spinning unit. It is also advantageous if the servicing apparatus is provided with an auxiliary drive for the rollers that can be applied to the rollers of a spinning unit. By means of this auxiliary drive, the rollers can be driven at a speed that is particularly suitable for yarn piecing. It is also expedient if the servicing apparatus is provided with means for actuating the valve of the vacuum source of a spinning unit. It thus becomes possible to switch off the suction effect during the piecing process and/or apportion it in such a way that suitable conditions exist for a yarn piecing process. For carrying out a yarn piecing process, it is also advantageous if the servicing apparatus is provided with an auxiliary drive that can be applied to the feeding and opening device of a spinning unit. It thus becomes possible, with the servicing apparatus, to apportion the feeding of the fiber material during the piecing process at a suitable ratio to the speed of the rollers, to the suction effect of the vacuum source, and to the withdrawal speed.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, embodiments constructed in accordance with the present invention.